Sanding device for curved surfaces

ABSTRACT

In a grinding apparatus with a rotor device driving an eccentrically mounted carrier device in which a shaft is mounted provided at one end with a head to which a supporting face for abrasive paper is fastened, facilitated grinding of curved surfaces by hand is obtained by the features that the supporting face is of curved design and has upper and lower sides with the same radius of curvature and is fastened to the head via an elastic element, and at least two guide devices are provided which cause the supporting face to be guided by the head reciprocatingly along a curved surface with the same radius of curvature as the supporting face.

CROSS REFERENCE TO RELATED APPLICATIONS

Applicants claim priority under 35 U.S.C. §119 of German Application No.198 33 814.7 filed Jul. 28, 1998. Applicants also claim priority under35 U.S.C. §120 of PCT/DE99/00082 filed Jan. 16, 1999. The internationalapplication under PCT article 21(2) was not published in English.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a grinding apparatus with a rotor devicedriving an eccentrically mounted carrier device in which a shaft ismounted provided at one end with a head to which a supporting face forabrasive paper is fastened.

2. The Prior Art

Grinding apparatuses of the abovementioned kind are used in the priorart in particular for grinding plane surfaces. For this purpose onefastens to the supporting face an abrasive paper which moves over thesurface to be ground due to the eccentric motion of the shaft mounted inthe carrier device in the form of superimposed harmonic oscillations,thereby subjecting said surface to a grinding process upon suitablebearing pressure of the abrasive paper. Difficulties always result withconventional grinding apparatuses when curved surfaces are to be groundsince the handling of a grinding apparatus is hindered by the fact thatonly pointwise contact of the plane abrasive paper on the curved surfaceis always given.

SUMMARY OF THE INVENTION

The problem of the invention is to provide a grinding apparatus forgrinding different curved surfaces with simple handling.

For a grinding apparatus of the abovementioned kind this problem issolved in that the supporting face is of curved design and has curvedupper and lower sides, the supporting face is fastened to the head viaan elastic element, and at least two guide devices are provided whichcause the supporting face to be guided by the head reciprocatingly alonga curved surface with the same radius of curvature as the supportingface.

Preferred embodiments of the invention are the object of the subclaims.

In the inventive grinding apparatus the feature that the supporting faceis of curved design and has curved upper and lower sides, the supportingface is fastened to the head via an elastic element, and at least twoguide devices are provided which cause the supporting face to be guidedby the head reciprocatingly along a curved surface with the same radiusof curvature as the supporting face, results in a grinding apparatuswherein the oscillating motion of the surface of its supporting face isforced along an imaginary curved surface having the same radius ofcurvature as the upper side of the supporting face due to the fact thatthe lower side of the supporting face has the same radius of curvatureas the surface of the supporting face and the lower side of thesupporting face is guided by at least two guide devices which arestationary with respect to the supporting face so as to preventoscillating motion lateral to the axis of the shaft mounted in thecarrier device and the lower side of the supporting face is guided uponlateral motion of the shaft with time-variant pressure against theparticular guide devices, in conjunction with an elastic elementprovided on the head of the shaft and interconnecting the supportingface and the shaft.

The abrasive paper to be used with the inventive abrasive paper supportapparatus is preferably applicable to the supporting face in replaceablefashion, for which purpose it is either formed as adhesive abrasivepaper or provided with integrated eyes cooperating with hooks providedon the supporting face or another place on the inventive apparatus. Tobe fastened to a spherically formed supporting face it is provided thatthe abrasive paper is formed not as a solid surface but like a rosettein order to ensure that no folds form in the paper.

According to a preferred embodiment of the inventive grinding apparatus,the guide devices are provided on the lower side of the supporting face.This obtains in simple and effective fashion the desired guiding effectof the supporting face by the guide devices. It is essential here thatthe guide devices act on a surface whose radius of curvature correspondsto that of the surface of the supporting face. One can thusfundamentally also conceive of embodiments of the inventive grindingapparatus in which the guide devices adjoin guide faces with anaccordingly provided radius of curvature which are spatially separatefrom the lower side of the supporting face but nevertheless mechanicallyconnected with the supporting face.

The guide devices of the inventive grinding apparatus are preferablyformed as ball-bearings, rolling bearings or slide bearings. Thisensures that the desired guiding effect of the guide devices on thelower side of the supporting face can be realized with low friction andlow material wear. Alternatively, the guide devices can be formed ascurved guide faces made of hard material with sliding ability, inparticular plastic material, and having a curvature adapted to the lowerside of the supporting face. This obtains the desired guiding effect ofthe guide devices on the lower side of the supporting face in anespecially cost-effective way.

According to further preferred embodiments of the inventive grindingapparatus, one can provide three, four or more guide devices. If atleast three guide devices are provided, an especially robust and exactguidance of the supporting face is obtained.

The elastic element connecting the supporting face with the shaftmounted in the carrier device is preferably formed as a spring, inparticular coil spring. This achieves the result that the lift of thesupporting face with respect to the head of the shaft caused by theeffect of the guide devices is compensated with a predeterminable,constant force, independently of the particular excursion of thesupporting face. Alternatively, the elastic element can be formed as adisk or ring made of elastic material, in particular rubber. It is onlyessential here that the lifting motion caused by the guide devicesbetween the head of the shaft and the supporting face due to thecurvature of the lower side of the supporting face is compensated withas little delay and as uniformly as possible.

The supporting face of the inventive grinding apparatus can havedifferent radii of curvature for different objects to be grounddepending on the embodiment. The supporting face can for example beformed cylindrically with a concave upper side for grinding convexsurfaces, or formed cylindrically with a convex upper side for grindingconcave surfaces. For grinding convex spherical objects the supportingface can be formed spherically with a concave upper side, and forgrinding concave spherical surfaces the supporting face can be formedspherically with a convex upper side.

If the supporting face is formed cylindrically, the guide devices arepreferably disposed axis-parallel to each other. If the supporting faceis formed spherically, four guide devices are preferably provided, beingdisposed in pairs at right angles to each other. The supporting face canalso be formed so as to have at least two different curvatures in two ormore planes.

The supporting face of the inventive grinding apparatus is preferablymade of hard material, in particular metal or hard plastic material. Forspecial cases of application requiring especially cautious grinding, thesupporting face formed of hard material can be mounted softly cushionedon a foamed plastic layer, or a foamed plastic layer can be provided onthe supporting face, or the supporting face itself can be made of softmaterial like wood or foamed plastic.

The inventive apparatus can have an additional eccentric device forcontrolling the motion of the supporting face further in presettablefashion. The additional eccentric device can be controllable with theaid of centrifugal forces and/or frictional forces. The additionaleccentric device permits the inventive apparatus to be advantageouslyexecuted such that the supporting face executes a variable motionresulting in a very fine grinding structure.

According to further preferred embodiments of the inventive apparatus,it may be provided that the eccentrically mounted carrier device, theshaft mounted therein or the head provided at one end thereof is mountedin a long hole which turns rotating motion of the particular componentinto one-dimensional linear oscillating motion. This achieves the resultthat the oscillating behavior of the supporting face of the inventiveapparatus is restricted in predetermined fashion, which leads to simplerhandling and is advantageous for certain grinding applications, inparticular when the surface to be ground is limited on one side byobstructing objects. The long hole can be disposed vertically so as toproduce horizontally extending oscillating motion, or it can be disposedhorizontally so as to produce vertically extending oscillating motion.

The inventive grinding apparatus will be explained in the following withreference to preferred embodiments shown in the figures of the drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a preferred embodiment of the inventive grinding apparatusin a cross-sectional view;

FIG. 2 shows a cylindrically shaped supporting face of the grindingapparatus shown in FIG. 1 in a view from the back;

FIG. 3 shows a spherically formed supporting face of the inventivegrinding apparatus in a view from the back.

FIG. 4 shows a further preferred embodiment of the inventive grindingapparatus in a cross-sectional view;

FIG. 5 shows the supporting face and head of the grinding apparatusshown in FIG. 4 in a view from the back.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT

Grinding apparatus 10 shown in FIG. 1 is provided with supporting face11 with lower side 11′ and upper side 11″in its central area withprojection 12 resembling a cylindrical pot with base surface 13 with gap13′ through which shaft 16 with head 15 is guided, head 15 having adiameter dimensioned greater than the diameter of shaft 16 and gap 13′and adjoining with its back 15′ rubber ring 14 supported against basesurface 13 of projection 12. Shaft 16 is pivotally mounted in bearingdevice 17 pivotally mounted off-center in body device 18. Body device 18is driven via shaft 19 mounted in bearing 20 and driven by a rotordevice not shown.

Guide devices formed as rolling bearings 21, 21′ are provided adjacentlower side 11′ of supporting face 11 to define the form of motion ofsupporting face 11 when the rotor device is turned on and shaft 19rotates. If rolling bearings 21, 21′ were absent, rotation of shaft 19would cause lateral motion of shaft 16 and thus via head 15 also ofsupporting face 11 reciprocatingly at right angles to longitudinal axis19′ of shaft 19. Rolling bearings 21, 21′ convert said lateral motioninto motion along a curved surface with the same radius of curvature assupporting face 11 due to the design of lower side 11′ of supportingface 11. This results in a lift of head 15 with respect to base surface13 of projection 12 which is absorbed elastically by rubber disk 14.

With supporting face 11 shown in FIG. 2, rolling bearings 21, 21′, 21″and 21′″ adjacent convexly formed lower side 11′ of supporting face 11are mounted with the aid of springs 22 and 23 so as to absorboscillations whose direction extends perpendicular to the double arrowsshown in FIG. 1 but nevertheless perpendicular to axis 19′ of shaft 19during operation of the inventive grinding apparatus. Supporting face 11therefore has two degrees of freedom during operation of the inventivegrinding apparatus, one allowing reciprocating motion along longitudinalaxis 111 of supporting face 11 and the other allowing reciprocatingmotion along a curved surface with the same radius of curvature assupporting face 11.

With spherically formed supporting face 11 shown in FIG. 3, rollingbearings 21, 21′, 21″ and 21′″ are disposed adjacent lower side 11′thereof, rolling bearings 21, 21′ and 21″, 21′″ being disposedaxis-parallel in pairs. Like the rolling bearings shown in FIG. 2,rolling bearings 21, 21′, 21″ and 21′″ shown in FIG. 3 are mountedreciprocatingly in springs 22, 23. This permits circular motion ofspherical supporting face 11 during operation of the inventive grindingapparatus.

In the embodiment of the inventive apparatus 10 shown in FIGS. 3 and 4,a cross-sectional view being shown in FIG. 4 and supporting face 11 andhead 25 shown in a view from the back in FIG. 5, shaft 28 of head 25 ismounted in vertically extending long hole 29 formed in component 27 andturning rotating motion of the particular component into linear,horizontally extending oscillating motion of head 25. The guide devicesare formed in this embodiment as guide faces 31, 31′ made of hardplastic material with sliding ability and have a curvature adapted tolower side 11′ of the supporting face. This embodiment of the inventiveapparatus is suitable in particular for grinding applications in whichthe surface to be ground is limited by obstructing objects on one side.

The above-explained examples of the invention serve merely the purposeof illustrating the inventive teaching given by the patent claims, whichas such is not restricted to the examples.

What is claimed is:
 1. A grinding apparatus with a rotor device drivingan eccentrically mounted carrier device in which a shaft is mountedprovided at one end with a head to which a supporting face for abrasivepaper is fastened, characterized in that the supporting face is ofcurved design and has curved upper and lower sides, the supporting faceis fastened to the head via an elastic element, and at least two guidedevices are provided which cause the supporting face to be guided by thehead reciprocatingly along a curved surface with the same radius ofcurvature as the supporting face.
 2. An apparatus according to claim 1,characterized in that the guide devices are provided on the lower sideof the supporting face.
 3. An apparatus according to claim 1,characterized in that the guide devices are formed as ball-bearings,rolling bearings or slide bearings.
 4. An apparatus according to claim1, characterized in that the guide devices are formed as curved guidefaces made of hard material with sliding ability, and have a curvatureadapted to the lower side of the supporting face.
 5. An apparatusaccording to claim 1, characterized in that three guide devices areprovided.
 6. An apparatus according to claim 1, characterized in thatthe elastic element is formed as a spring.
 7. An apparatus according toclaim 1, characterized in that the elastic element is formed as a diskor ring of elastic material.
 8. An apparatus according to claim 1,characterized in that the supporting face is formed cylindrically with aconvex upper side.
 9. An apparatus according to claim 8, characterizedin that the guide devices are disposed axis-parallel to each other. 10.An apparatus according to claim 8, characterized in that the supportingface is formed so as to have at least two different curvatures in two ormore planes.
 11. An apparatus according to claim 1, characterized inthat the supporting face is formed cylindrically with a concave upperside.
 12. An apparatus according to claim 1, characterized in that thesupporting face is formed spherically with a convex upper side.
 13. Anapparatus according to claim 12, characterized in that four guidedevices are provided which are disposed in pairs at right angles to eachother.
 14. An apparatus according to claim 1, characterized in that thesupporting face is formed spherically with a concave upper side.
 15. Anapparatus according to claim 1, characterized in that the supportingface is made of hard material.
 16. An apparatus according to claim 1,characterized in that the curved upper and lower sides of the supportingface have a radius of curvature dimensioned such that the upper andlower sides have a common summit.
 17. An apparatus according to claim 1,characterized in that an additional eccentric device is provided forcontrolling the motion of the supporting face further in presettablefashion.
 18. An apparatus according to claim 17, characterized in thatthe additional eccentric device is controllable via centrifugal forcesand/or frictional forces.
 19. An apparatus according to claim 1,characterized in that the eccentrically mounted carrier device, theshaft mounted therein or the head provided at one end thereof is mountedin a long hole which turns rotating motion of said eccentrically mountedcarrier device, shaft mounted therein or head into one-dimensionallinear oscillating motion.
 20. An apparatus according to claim 19,characterized in that the long hole is disposed vertically and produceshorizontally extending oscillating motion.
 21. An apparatus according toclaim 19, characterized in that the long hole is disposed horizontallyand produces vertically extending oscillating motion.